Mechanical energy from the environment (e.g. ambient vibrations or activities of the human body) represents a unique and sustainable energy source suited for powering portable electronics and unattended devices. In 2012, the triboelectric nanogenerator (TENG) was first reported as a new type of technology that converts environmental mechanical energy into electrical energy. (See, F.-R. Fan, Z.-Q. Tian, Z. Lin Wang, Nano Energy 2012, 1, 328 and F. R. Fan, J. Luo, W. Tang, C. Li, C. Zhang, Z. Tian, Z. L. Wang, Journal of Materials Chemistry A 2014, 2, 13219.) Compared to other technologies, TENGs are advantageous in terms of their high efficiencies, high power densities, light weight, low cost, and manufacturability. A TENG functions under the coupling effects of contact electrification and electrostatic induction. The working principle requires two dissimilar surfaces to be oppositely charged upon contact. The common positive materials in TENGs are polyamides, metals, indium tin oxide (ITO), and zinc oxide. Common negative materials include fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), and polyethylene terephthalate (PET). The positive and negative materials are used in pairs in TENGs due to their opposite tendencies to gain or lose charges upon contact.